At present, an electric vehicle using a motor as a drive source for vehicle travel is being developed by not only automobile makers but also many companies and organizations. To drive a motor, an in-vehicle power supply having high voltage of hundreds volts is necessary. The power supply is realized by a battery system using an assembled battery constructed by coupling a number of battery cells (unit cells) each generating a voltage of a few bolts in series. In such a battery system, states of each battery cell (for example, battery voltage, battery impedance, temperature, charge remaining amount, and the like) have to be monitored in all of use environments at the time of travel of a vehicle, charging, and the like. Since a battery system has a severe risk such as firing or explosion at the time of occurrence of a failure, to safely operate it, state data of battery voltage and the like of each of a plurality of battery cells measured in a voltage measuring device have to be transferred to a system control apparatus and calculated in a real-time manner, and a proper control has to be performed on the basis of the state data.
To monitor the states of each of battery cells, a battery control system is configured. The battery control system is to monitor and control each of the battery cells with high precision. The battery control system is usually constructed by a monitoring IC (Integrated Circuit), a fault monitor IC, an MCU (Micro Controller Unit) operating as a system control unit, and the like.
The monitoring IC monitors the states of a battery cell and outputs state data (mainly, battery voltage). The monitoring IC measures the battery voltage of a battery cell with precision of, for example, about ±5 mV and outputs a measurement result in accordance with an instruction from the MCU. The fault monitor IC monitors the voltage of the battery cell and, in the case where the monitored voltage exceeds predetermined voltage, outputs a signal. For example, the fault monitor IC outputs a signal indicative of an over discharge state in the case where the battery voltage becomes 2V or less and outputs a signal indicative of an overcharge state in the case where the battery voltage becomes 4.5V or higher. The MCU controls the monitoring IC and the fault monitor IC and, on the basis of output results of the monitoring IC and the fault monitor IC, controls the battery control system. The MCU calculates the state data output from the monitoring IC in a real-time manner and performs a proper control on the basis of the state data.
The monitoring IC and the fault monitor IC usually have the function of monitoring a lithium (Li) ion battery in which 12 to 14 cells are coupled in series. A battery monitoring module is constructed by a module substrate on which one monitoring IC, one fault monitor IC, and peripheral elements are mounted and 12 to 14 battery cells coupled in series. Therefore, for example, in the case of a Li ion battery, an output of one battery monitoring module is about 43.2V to 50.4V. Consequently, an assembled battery of hundreds volts is constructed by stacking a plurality of battery monitoring modules. The plurality of (for example, eight) battery monitoring modules stacked are controlled by a single MCU. The MCU controls the battery monitoring modules individually by communication lines coupling the monitoring ICs of the plurality of battery monitoring modules in parallel or in series.
To individually control the battery monitoring modules by the MCU, for example, an address has to be set in each of, for example, eight monitoring ICs stacked. For this purpose, many monitoring ICs have a plurality of pins for setting addresses. By changing coupling (pull-down/pull-up) of the pins, an address is set. For example, in the case of eight monitoring ICs stacked, at least three address setting pins are necessary.
Patent literature 1 discloses an electricity storage system provided with an address recognizing device having an address detection pin to which analog current is supplied and specifying the address of an electricity storage module on the basis of the direction and magnitude of the supplied current. A plurality of electricity storage modules (B1 to B14) each obtained by coupling a plurality of electricity storage cells (E1 to E10) in series or in parallel are coupled in series or in parallel via coupling pins (11a, 12a), an address detection pin (S1) is provided for each of the electricity storage modules, and the address detection pins are mutually coupled. The address detection pins (S1) in the electricity storage modules (B1 to B14) are short-circuited by a cable (6), and the cable (6) is coupled to the ground. With the configuration, the directions of currents flowing from discharge lines (21) into a current detection circuit (23) from the electricity storage module (B1) toward the electricity storage module (B14) become constant. Only by comparing the magnitudes, an address can be specified. In the electricity storage system, according to a signal of an amount of the current of the current detection circuit (23) transmitted from a control circuit (M) via pins (S2 and S3) of a transformer (5) on the basis of a voltage signal received by a microcomputer, addresses are automatically assigned to the electricity storage modules (B1 to B14) by a host computer.
Patent literature 2 discloses an assembled battery in which a plurality of unit cell boards and a battery management unit are coupled by a loop communication path. The unit cell board is provided for each unit cell, digitizes measurement values such as voltage, internal resistance, and temperature of the unit cell, ambient temperature, and the like, holds the values, and transmits them to the battery management unit in accordance with a token-ring communication control protocol. Since the communication path has a loop shape, most of couplings are between the adjacent unit cell boards. Since the potential difference between the adjacent unit cells is not large, the configuration of a level shift circuit is simple.
Patent literature 3 discloses an electricity storage apparatus having master-side control means (23) controlling the electricity storage apparatus and a plurality of slave-side control means (14) monitoring battery voltage. The electricity storage apparatus stores the address of itself which is set by process operations of the master-side control means (23) and each of the slave-side control means (14) into a storage unit, adds the address of itself to a control signal based on the battery voltage detected by a voltage detection circuit (13), and transmits the resultant signal to the master-side control means (23).
The slave-side control means (14) is constructed by, for example, a microcomputer to which a signal of the battery voltage transmitted/received to/from a control unit (1) and another assembled battery (5) via a communication interface circuit (12) and detected by the voltage detection circuit (13). In the case where the battery voltage detected by the voltage detection circuit (13) exceeds a limit voltage value of a secondary cell (3), the slave-side control means (14) recognizes the fact. As will be described later, a control signal as failure information is transmitted with the address which is set to the control unit (1) via the communication interface circuit (12). Consequently, the control unit (1) can specify and recognize the assembled battery having the failure. The slave-side control means (14) has a random-number generating unit (15) for generating a temporary address and a storage unit (16) for storing a set address.
The slave-side control means (14) receives the command, performs a command receiving process (step 50), and determines the kind of the command (step 51). In the case where it is determined by the determination that the command is an address resetting command, a random number of 1 to N or less (N is a predetermined upper limit value and is 255 in this case) is generated by using the random-number generating unit (15) (a random number generation program using battery voltage detection data as a seed) held in the slave-side control means (14), and the random number is set as a temporary self address (step 52) Subsequently, the slave-side control means (14) prepares return data (step 53), counts the temporary address as wait time, performs a process of adjusting return wait time by the employed random number (step 54), performs a process of returning the temporary address, and transmits the temporary address to the master-side control means (23) (step 55). The master-side control means (23) which receives the temporary address transmitted from the slave-side control means (14) performs a process of receiving the temporary address (step 41) and determines whether the number of pieces of valid reception data is the same as the number of kinds of temporary addresses or not (step 42). In the case where the number of pieces of valid reception data and the number of kinds of temporary addresses are not the same in the determination in step 42, the master-side control means (23) returns to step 40, issues an address resetting command, and repeats the operation until the number of pieces of valid reception data and the number of kinds of the temporary address become the same for the following reason. On the side of the master-side control means (23), when all of the slave-side control means (14) have different temporary addresses, the number of pieces of valid reception data and the number of kinds of temporary addresses are supposed to finally become the same. In the case where the number of pieces of valid reception data and the number of kinds of temporary addresses become the same in step 42, the master-side control means (23) determines whether there is overlap in the temporary addresses or not (step 43). In the case where there is overlap in the temporary addresses in the determination, the master-side control means (23) returns to step 40, issues the address resetting command, and repeats the operation until there is no overlap in the temporary addresses. When there is no overlap, on assumption that different address data is distributed to all of the slave-side control means (14), the master-side control means (23) issues an address determination command, and transmits it to all of the slave-side control means (14). The slave-side control means (14) receives the transmitted address determination command, performs a command receiving process (step 50), and determines the kind of the command (step 51). In the case where the command is determined as the address determination command by the determination, the slave-side control means (14) stores the temporary address as the genuine self address of the master-side control means (23) into a storing unit 16 (step 56), and performs the processes in step 53 to step 55. In such a manner, the addresses of the plurality of battery monitoring devices 2 can be automatically determined. By generating a temporary address from the random-number generating unit (15) and performing the process to determine the temporary address as the self address as described above, the self address can be easily set in each of the battery monitoring devices (2).
Patent literature 4 discloses a system having a central processing unit (1) and a plurality of input/output units (2 to 5) coupled by a system bus (6), in which an address is automatically set in the input/output units. The central processing unit (1) and the plurality of input/output units (2 to 5) are coupled by a daisy-chain data line (7). First, an address for automatically setting addresses is set in the system. The address is designated, and the central processing unit (1) transmits the head value of an address to be set to the input/output unit (2) at the first stage in the daisy-chain data line (7). The input/output unit (2) at the first stage sets the received address, adds an address of the amount of the memory of the unit itself, and transmits the head value of an address to be set to the input/output unit (3) at the next stage. By repeating the operation up to the input/output device (5) at the final stage, the addresses of the input/output units (2 to 5) can be mapped.